1. Field of the Invention
This invention relates generally to a method for packaging semiconductor devices in an implantable device, and, more particularly, to a method and apparatus for providing electrical connectivity between a plurality of stacked semiconductor devices in an implantable device.
2. Description of the Related Art
Electronic devices that monitor or otherwise interact with human bodies have been in widespread use for some time now. For example, electronic devices and sensors have been routinely used to measure muscular activity. That is, electronic devices are commonly used to detect and graph electrical activity representative of a beating human heart. Electrocardiograms (EKGs), which are produced by such electronic devices, are routinely used by doctors and/or technicians as diagnostic aids to evaluate the condition of a patient""s heart.
These types of electronic devices have proven to be accurate and reliable in operation, but initially were generally limited to monitoring the heart, as opposed to controlling or assisting the heart, owing principally to their size and power requirements. Outside the laboratory or hospital these electronic monitors did not prove useful in controlling the activity of the human body, such as the heart. Rather, these electronic devices became more useful in controlling or assisting in the proper operation of the heart, as they became portable, and preferably implantable within the human body.
With the development of relatively small, low-power semiconductors, implantable pacemakers became viable. As pacemakers have become more sophisticated, monitoring more functions and implementing more sophisticated control techniques, their complexity has increased dramatically. Increased functionality and complexity have lead to more complex, and thus, larger circuitry. Implantability of these devices, however, suffers with increased size. That is, smaller devices are easier to implant. Moreover, smaller implantable devices are generally more efficient to operate, have longer battery life, and are more readily accepted by the patient and doctor.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.
In one aspect of the present invention, a method for forming a stackable wafer in an implantable device is provided. The method comprises forming an opening extending substantially through the wafer. Insulator material preferably of the oxide or nitride type is placed in the hole using known processes in the art. Thereafter, conductive material is deposited within the opening to substantially fill the opening. A bump is then formed on an upper surface of the wafer adjacent the conductive material, and a contact pad is formed on a lower surface of the wafer adjacent the conductive material.
In another aspect of the present invention, a method for forming a stacked arrangement of a first and second wafer in an implantable device is provided. The method comprises forming an opening extending substantially through the first wafer. Insulator material preferably of the oxide or nitride type is placed in the hole using known processes in the art. Thereafter, conductive material is deposited within the opening to substantially fill the opening in the first wafer. A bump is then formed on an upper surface of the first wafer adjacent the conductive material, and a contact pad is formed on a lower surface of the first wafer adjacent the conductive material. The method further comprises forming an opening extending substantially through the second wafer. Thereafter, conductive material is deposited within the opening to substantially fill the opening in the second wafer. A bump is then formed on an upper surface of the second wafer adjacent the conductive material, and a contact pad is formed on a lower surface of the second wafer adjacent the conductive material. The first wafer is positioned adjacent the second wafer with the bump of the first wafer being adjacent the contact pad of the second wafer. The bump of the first wafer is then coupled with the contact pad of the second wafer.